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Highlights This paper investigates how combining natural and synthetic fibers within yarns, altering the degree of hybridisation, and varying weave architectures affect the homogenized elastic properties and stress distributions in 2D woven composite laminae using a two‐scale homogenization scheme. The novelty lies in integrating a micro‐scale representative volume element model with a meso‐scale repeating unit cell model to capture intra‐yarn natural/synthetic fiber hybridisation. The study focuses on 2/2 twill and 5‐harness satin woven laminae with flax/E‐glass, hemp/E‐glass and basalt/E‐glass hybrid yarns, all with a total fiber volume fraction of 0.6. Fiber distributions are created through a random sequential expansion algorithm for hybrid RVEs, while periodic meso‐structures are used to define weave architectures for RUCs. Results show that yarn‐level fiber hybridisation significantly influences matrix stress distributions, with variations of up to 22%. In contrast, weave architecture has a minimal effect, with variations in homogenized properties below 2%. Varying fiber types, degrees of hybridisation and weave architectures allow for the tailoring of yarn and lamina properties and altering the stress distributions at micro‐ and meso‐scales and potentially influencing damage mechanisms. The modeling approach for analyzing the mechanical behavior of intra‐yarn hybrid natural/synthetic woven laminae could potentially be used to tailor their tolerance to damage. Two‐scale homogenization integrates RVE and RUC for 2D woven hybrid composites. Analyzed flax/E‐glass, hemp/E‐glass, basalt/E‐glass in twill and satin weaves. Intra‐yarn hybridisation significantly affects properties and stress fields. Hybridizing fibers offers tailored properties and may improve damage tolerance. [ABSTRACT FROM AUTHOR]

The custom design of a composite material requires the knowledge of its effective behavior which depends on several parameters such as the properties of the constituents, their distributions, shapes and sizes. In thermal conductivity, all these parameters have a direct and significant influence on the effective thermal conductivity (ETC) of composites. These parameters act differently on the behavior of the composite according to its use as much as a good conductor by improving its ETC or by reducing it by considering it as an insulator. The main goal of this work is an extensive study of all possible situations of ETC by a numerical homogenization technique based on the Finite Elements Method. For this purpose, the two main categories of composites, namely the periodic composites represented by the unit cell and the random RVE, are considered. For each category of composite, different contrasts, different particles' volume fractions, aspect ratios, positions, and orientations are studied. In order to ensure the simulation results are effective and representative, two boundary conditions, namely Uniform Temperature Gradient Boundary Conditions (UGT) and Periodic Thermal Boundary Conditions (PBC), were imposed on all considered microstructures. The results of this study constitute a synthesis of the effective thermal conductivities of all the possible situations which can be summarized as follows: On the one hand, the reinforcements shape effect is very important irrespective of the nature of the periodic and random composites and on the other hand, the two types of composites do not have the same behavior as that for the reinforcements with a circular or almost circular shape. This study also emphasizes the situations where the ETC can be estimated analytically and when homogenization is necessary. From a practical point of view, and on the basis of the obtained results, this study made it possible to show clearly in which situation the composite becomes more conducting and in the opposite case when it becomes more insulating. [ABSTRACT FROM AUTHOR]

This study employs a microstructure-based finite element modeling approach to understand the mechanical behavior of asphalt mixtures across different length scales. Specifically, this work aims to develop a multi-scale modeling approach employing representative volume elements (RVEs) of optimal size; this is a key issue in asphalt modeling for high-fidelity fracture modeling of heterogeneous asphalt mixtures. To determine the optimal RVE size, a convergence analysis of homogenized elastic properties is conducted using two types of RVEs, one made with polydisperse spherical inclusions, and another made with polydisperse truncated cylindrical inclusions, each aligned with the American Association of State Highway and Transportation Official's maximum density gradation curve for a 12.5 mm Nominal Maximum Aggregate Size (NMAS). The minimum RVE lengths for this NMAS were found to be in the range of 32–34 mm. After the optimal RVE size for each inclusion shape is obtained, computational models of heterogeneous Indirect Tensile Asphalt Cracking Test samples are then generated. These models include the components of viscoelastic mastic, linear elastic aggregates, and cohesive zone modeling to simulate the rate-dependent failure evolution from micro- to macro-cracking. Examination of load-displacement responses at multiple loading rates shows that both heterogeneous models replicate experimentally measured data satisfactorily. Through micro- and macro-level analyses, this study enhances our understanding of the composition-performance relationships in asphalt pavement materials. The procedure proposed in this study allows us to identify the optimal RVE sizes that preserve computational efficiency without significantly compromising their ability to capture the asphalt material behavior under specific operational conditions. [ABSTRACT FROM AUTHOR]

A micromechanical model implemented with the finite element method (FEM) using the representative volume element (RVE) approach is developed to investigate the creep compliance behavior of carbon nanotube (CNT)-polymer nanocomposites. Effects of the CNT waviness, orientation, volume fraction and aspect ratio on the creep compliance of the nanocomposite are examined. Contribution of the interphase region formed due to the interaction between CNTs and matrix to the nanocomposite creep behavior is considered. The nanocomposite creep behavior is affiliate on the waviness and orientation of CNTs. Increasing the volume fraction and length of CNT and interphase thickness improves the nanocomposite creep performance. [ABSTRACT FROM AUTHOR]

The properties of unidirectional (UD) composites has been investigated by analyzing their elastic and strength characteristics under shear loading. The UD fiber‐reinforced polymer (FRP) composites usually consist of fibers randomly dispersed throughout the cross‐section in the transverse direction which is generally not accounted for. A micromechanical model based on finite element analysis (FEA) approach is utilized here to examine these properties. The study begins by identifying micro scale unit cells or repetitive unit cells (RUCs) at the micro scale, as well as representative volume elements (RVEs). The distribution of fiber volume fraction (Vf) varies among various micro scale unit cells positioned in the transverse cross‐section. The elastic properties and strength are estimated by considering the properties of the matrix and fibers, and the configuration of micro scale unit cells, which feature a fiber arrangement which is categorized as hexagonal and varying Vf at different locations (from 0.35 to 0.75). However, the overall Vf for the UD composite remains constant at 0.65. Studies are also carried out with the random distribution of fibers at micro scale unit cells. The findings reveal that the random distribution of fibers significantly impacts the shear behavior of the composite. This investigation provides valuable insights into how the mechanical properties of the UD composite are subjective by the distribution of fiber, thereby contributing to the design and development of this light weight high‐performance material. Highlights: Elastic and strength analysis of UD composites is presented.Emphasis is on fiber dispersion in transverse plane.Microscale unit cells, RUCs and RVE are identified.Studies are carried out based on micromechanical model.Influence of fiber distribution on shear behavior is investigated. [ABSTRACT FROM AUTHOR]

Copyright of Polymer Materials Science & Engineering is the property of Sichuan University, Polymer Research Institute and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The skin is the largest organ in the human body and serves various functions, including mechanical protection and mechanosensation. Yet, even though skin's biomechanics are attributed to two main layers—epidermis and dermis—computational models have often treated this tissue as a thin homogeneous material or, when considering multiple layers, have ignored the most prominent heterogeneities of skin seen at the mesoscale. Here, we create finite element models of representative volume elements (RVEs) of skin, including the three-dimensional variation of the interface between the epidermis and dermis as well as considering the presence of hair follicles. The sinusoidal interface, which approximates the anatomical features known as Rete ridges, does not affect the homogenized mechanical response of the RVE but contributes to stress concentration, particularly at the valleys of the Rete ridges. The stress profile is three-dimensional due to the skin's anisotropy, leading to high-stress bands connecting the valleys of the Rete ridges through one type of saddle point. The peaks of the Rete ridges and the other class of saddle points of the sinusoidal surface form a second set of low-stress bands under equi-biaxial loading. Another prominent feature of the heterogeneous stress pattern is a switch in the stress jump across the interface, which becomes lower with respect to the flat interface at increasing deformations. These features are seen in both tension and shear loading. The RVE with the hair follicle showed strains concentrating at the epidermis adjacent to the hair follicle, the epithelial tissue surrounding the hair right below the epidermis, and the bulb or base region of the hair follicle. The regions of strain concentration near the hair follicle in equi-biaxial and shear loading align with the presence of distinct mechanoreceptors in the skin, except for the bulb or base region. This study highlights the importance of skin heterogeneities, particularly its potential mechanophysiological role in the sense of touch and the prevention of skin delamination. [ABSTRACT FROM AUTHOR]

The objective of this study is to improve the mechanical properties of self-healing carbon fiber reinforced polymer (CFRP) with microcapsules (MCs) incorporating healing agents, in order to achieve superior mechanical properties and healing efficiency. The approach to improve the mechanical properties is to hybridize spread carbon fiber (SCF) and woven carbon fiber (WCF) as reinforcements. The interlaminar shear strength and the healing efficiency of the self-healing SCF/WCF hybrid laminates were evaluated by short beam shear tests, and then compared with those of self-healing SCF/EP laminates and self-healing WCF/EP laminates. Moreover, the finite element analysis (FEA) using a representative volume element (RVE) model of the SCF/WCF hybrid laminates containing MCs was performed to evaluate the elastic properties and the internal stress and reveal the relation between them and microstructure. Furthermore, we performed the FEA of short beam shear test using the elastic properties predicted from the RVE models and verified the validation of the RVE model by comparing the analytical results with the experimental results. The experimental results showed that the hybridization of SCF and WCF can be effective for improving mechanical properties of self-healing CFRP laminates compared to those of self-healing SCF/EP laminates. However, the self-healing SCF/WCF hybrid laminates did not present sufficient healing efficiency due to the large transverse cracks in the WCF layers. Therefore, in order to improve healing efficiency, it is necessary to suppress the large crack propagation in the WCF layer. The analytical results indicated that the stress concentration occurred in the WCF layer and could be mitigated by increasing the thickness of the SCF layer. The experimental results and analytical results were in good agreement. Therefore, the RVE model used in this study effectively predicted the properties of the self-healing CFRP laminates and provided microstructure design guidelines for achieving superior mechanical properties and healing efficiency.

This article characterized the mechanical performance and failure mode of single‐lap joints (SLJs) of carbon fiber reinforced boron‐modified phenolic resin plastic (CF/BPR) and TC4 titanium alloy by quasi‐static tensile tests at four temperatures (25, 100, 175, and 250°C). The experimental results indicated that the shear strength of SLJs is 10.8 MPa at 25°C, which experiences monotonic drop to 80%, 42.6%, and 18.5% with temperature increase from 100 to 175°C, and to 250°C, respectively. Additionally, there was a transformation in the failure mode from composite material failure to cohesive failure in the adhesive along with the temperature increase. The intralaminar elasticities of CF/BPR were predicted using representative volume element (RVE), and the mechanical properties of three types of bondlines (i.e., the interlamination, interface of CF/BPR and the epoxy adhesive layer) were determined by both experiment and predictive methods. A finite element model taking into account the intralaminar damage of CF/BPR and the cohesive behavior of three bondlines was established. The simulated results showed good consistency with the experimental data for failure prediction, and the mechanical performance and damage propagation of SLJs at different temperatures were discussed. This research provides reference for the design and manufacture of high‐temperature bonded structures. Highlights: RVE and degradation factor methods evaluate the elasticity of composite material.Four types of damage behaviors are considered in the established FE model.The SLJs exhibit single or multiple failure modes at different temperatures.The mechanical properties of SLJs severely degraded with increasing temperature. [ABSTRACT FROM AUTHOR]

Semi-flexible pavement (SFP) material is a composite comprising cement, coarse aggregates and asphalt mortar, which has complex mechanical properties. Traditional experimental methods struggle to accurately quantify the effect of each phase and their interfaces on the SFP's mechanical properties. Micromechanical modelling based on finite element method offers a promising solution. In this study, a new micromechanical model for SFP is proposed, idealizing the material by representative volume elements. SFP mesostructure is represented as a simplified five element composite consisting of cement, asphalt mortar, aggregate, pore and cement-asphalt mortar interface. Periodic boundary conditions are used to simulate an infinite repetitive structure within a finite computational domain. The resulting model allows evaluating the stiffness and damage resistance of SFP in a computationally efficient manner. This model is utilized to explore the mechanical properties of SFPs and the results are compared with the experimental findings. The results show that the model captures the uniaxial compressive strength and stiffness for all materials examined. The model is further used to evaluate the effect of properties of individual elements of SFP on its stiffness and strength. The feasibility of using the proposed modelling approach to optimize the material design of SFP is discussed.

The present study provides a thorough analysis of the influence of filament orientation on the tensile stiffness of 3D-printed structures. This exploration employs a combination of numerical simulations and experimental trials, providing an extensive understanding of additive manufacturing, particularly 3D printing. This process involves layer-by-layer material deposition to produce three-dimensional objects. The examination specifically targets PLA-based 3D printed structures created using Fused Filament Fabrication (FFF) technology and subjects them to rigorous evaluations using a universal tensile testing machine. Additionally, this approach combines Representative Volume Element (RVE) and Classical Lamination Theory (CLT) techniques to extrapolate the mechanical properties of the test material. Although the initial methodology faces challenges in determining the shear modulus with precision, an in-depth investigation results in enhanced accuracy. Furthermore, this study introduces a parametric RVE numerical method, demonstrating its resilience in handling sensitivity to shear modulus. A comparative study of results derived from both the analytical methods and experimental trials involving five series of samples with varied layups reveals that the newly proposed numerical method shows a stronger correlation with the experimental outcomes, delivering a relative error margin of up to 8%. [ABSTRACT FROM AUTHOR]

The performance of fiber‐reinforced composites is not only determined by their constituents, but also by the spatial distribution of inclusions. The traditional random distribution algorithm only considers the randomness of its relative position, and every newly generated fiber has to be checked with all the existing fibers, which requires a large amount of calculation. In this paper, inspired by the spreading process that the fibers are not arranged randomly, but the forces acting on the upper and lower rows of fibers. A random fiber distribution algorithm based on partition randomness is proposed, and a microscopic model of in‐plane fibers with random distribution is established. The maximum volume fraction of fibers generated by the algorithm is 75%, and the generation time is less than 20s. Statistical characterization and finite element analysis of the structure generated by the algorithm are compared with the experimental data to verify the randomness and effectiveness of fibers. The algorithm overcomes the jamming limit of the traditional hard‐core method, and can efficiently generate random microstructure models with different volume fractions, which can be a promising alternative for modeling and analysis of unidirectional fiber‐reinforced composites. [ABSTRACT FROM AUTHOR]

A homogenization method for the vibration analysis of periodic sandwich panels is presented. Periodic boundary conditions are applied to a representative volume element (RVE) of the structures. The complex responses of the RVE under eight sinusoidal excitations are calculated and the complex stiffness matrix of the sandwich panels is obtained by the direct-solution steady-state dynamic analysis (DSDA) using the finite element method (FEM) in the frequency domain. Based on equivalent single-layer (ESL) theory and finite element-modal strain energy (FE-MSE) method, the natural frequencies, the mode shapes and the loss factors of the structures are obtained by shell models. The effectiveness of the homogenization method is validated by using pyramidal lattice truss sandwich panels made of carbon fiber reinforced plastics (CFRP). The results obtained by the homogenization method are compared with those obtained by experiments and solid models. The effects of the number of cells and damping layers are discussed. [ABSTRACT FROM AUTHOR]

In this paper, a void closure model applicable to the general hot forming process has been proposed. Through the representative volume element (RVE) method, the influences of void shape, orientation, and stress state on void closure tendency were analysed. The void closure model was established so that it could consider these cross effects. The model calculates the changing void radius and orientation during deformation by considering the rate of change of the parameters affecting void deformation with respect to the effective strain. The model predicted the void closure tendency well on the RVE scale and predicted the void closure adequately in a multi-stage process with random voids. The results were compared with the stress-triaxiality-based (STB) model, which showed that the void closure model proposed in this study is applicable in general situations. A cogging process was analysed, and the degree of void closure at the end of each pass was compared with the calculated results of the void closure model. For the experimental verification of the proposed model, spherical and ellipsoid voids were placed in a rectangular specimen, and the radii of the voids after compression were measured. The measurement results were compared with the calculation results of the proposed model. [ABSTRACT FROM AUTHOR]

This work presents a computational study on the impact of carbon nanotube (CNT) enriched matrix on the performance of 1–3 lead-free piezoelectric periodic composites. Specifically, we investigate a piezoelectric composite system consisting of x 3 parallel aligned fibers of polycrystalline barium titanate (BaTiO3) embedded in a polydimethylsiloxane (PDMS) matrix doped with multiwalled CNT. The effective properties and several figures of merit have been obtained to evaluate the performance of this composite system as is typically done for these materials used for sensing, actuating, or harvesting applications. The results reveal that, in lead-free BaTiO3/PDMS piezocomposites, the addition of CNTs in the PDMS matrix should be f CNT ≈ 0. 5 f c "being f c the percolation threshold", but not higher. In another case, we will only improve the performance of the lead-free piezocomposite for sensing or actuating, but not for energy harvesting applications. This study provides insights into the use of multiwalled CNTs in lead-free piezocomposites and suggests the optimal concentration of CNTs to enhance their performance. The findings have potential implications for the development of new piezoelectric materials and devices for sensing and harvesting applications. [ABSTRACT FROM AUTHOR]

A new phase-field based method is proposed to represent the graphene reinforced composites and investigate the mechanical properties of the nanocomposites. The discrete graphene flakes are now represented with a continuous phase-field ϑ (x). Considering the extremely large aspect ratio of the graphene, both isotropic and anisotropic constitutions are used for the material at the transition region between the graphene and epoxy matrix. The present model is validated through comparison with shell based finite element model for the anisotropic constitution. The present model offers a simple way to model the thin flakes with a large aspect ratio reinforced composites in FEM software. [ABSTRACT FROM AUTHOR]

In this paper, a multiscale analysis method was proposed to simulate carbon nanoparticles (CNPs)−filled polymers which can be strain sensors applied in wearable electronic devices, flexible skin, and health monitoring fields. On the basis of the microstructure characteristics of the composite, a microscale representative volume element model of the CNPs−filled polymer was established using the improved nearest−neighbor algorithm. By finite element analysis, the variation of the junction widths of adjacent aggregates can be extracted from the simulation results. Then, according to the conductive mechanism of CNP−filled polymers, the composite was simplified as a circuit network composed of vast random resistors which were determined by the junction widths between adjacent aggregates. Hence, by taking junction widths as the link, the resistance variation of the CNPs−filled polymer with the strain can be obtained. To verify the proposed method, the electromechanical responses of silicone elastomer filled with different CNPs under different filling amounts were investigated numerically and experimentally, respectively, and the results were in good agreement. Therefore, the multiscale analysis method can not only reveal the strain−sensing mechanism of the composite from the microscale, but also effectively predict the electromechanical behavior of the CNPs−filled polymer with different material parameters. [ABSTRACT FROM AUTHOR]

It is significant to determine the macroscopic mechanical properties of composite materials with complex microstructure efficiently and accurately in many fields. We propose a deep learning method based on three-dimensional convolutional neural network (3D CNN) to predict the elastic coefficients of composite materials with inclusions of arbitrary sizes, shapes and material parameters. 3D datasets are generated, and a storage algorithm is proposed to reduce great storage costs in 3D. A general framework for 3D CNN models is constructed, and numerical experiments are carried out using 3D CNNs of various scales. Our results demonstrate that the scale of full connection part is the key factor of prediction ability of 3D CNNs in this task. We also demonstrate that our method can effectively save computational time compared with traditional numerical methods such as the finite element method in large-scale prediction tasks. [ABSTRACT FROM AUTHOR]

Copyright of Acta Materiae Compositae Sinica is the property of Acta Materiea Compositae Sinica Editorial Department and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

In this paper, the modulus prediction of NP-C/C is completed by establishing a multiscale finite element model, and the influence weight analysis of the modulus is carried out by using the analytical homogenization method. Firstly, three Micro-RVE, including unidirectional composites, short fiber reinforced composites and porous matrix, are established to characterize the layers of NP-C/C. Then, the finite element model is used for homogenization and passed upward into Meso-RVE, and the modulus prediction is completed. Finally, the analytical homogenization method is used combined with the MATLAB® script to analyze the influence weight of the modulus by adjusting the parameters. The results show that the average errors of stiffness coefficient prediction values obtained based on the analytical homogenization method are only 6.0% relative to the experimental values, which are lower than 25.3% of the finite element model. The modulus prediction method given in this study does not need to establish a micromechanical model with complex structure, and can be directly completed by computer script when the prediction accuracy is met, which is simple and feasible. [ABSTRACT FROM AUTHOR]

The mechanical response of dual phase (DP) steel exhibits a complex dependence on the microstructure. The chemical composition and microstructure characteristics of the phases have significant effects on the contrast between the response of the phases, which affects, not only the strength and ductility, but also the anisotropic response of DP steel under strain path changes. In this work, extended dislocation-based models of the ferrite and martensite phases of DP steel are proposed and used in a finite element based representative volume element approach to account for the contrast between the local response of the phases. The flow stress of each phase is computed as a function of the amount of substitutional and interstitial solute elements and the microstructural characteristics of the phase. Particular attention is paid to the phase model of the martensite phase. The model parameter controlling the storage of dislocations is related to the carbon content, which appears to be the most important parameter affecting the strength of martensite and its contrast with the local response of the ferrite phase. The model predicts a significant effect of the contrast between the local responses of the phases and the microstructure characteristics of each phase on the yield locus after prestraining and on the stress–strain behaviour after strain path change, i.e., forward-reverse shear loading and cyclic uniaxial tension–compression loading. [ABSTRACT FROM AUTHOR]

The engineering design of metamaterials with selected acoustic properties necessitates adequate prediction of the elastic wave propagation across various domains and specific frequency ranges. This study proposes a systematic approach centered on the finite element characterization of the three-dimensional Green's function for a representative volume element. The inherent characteristics of broadband waves and singular impulses contribute to notable challenges related to accuracy and high-frequency oscillations, and thus the emphasis is set on providing an exhaustive analysis for this numerical characterization scheme. The study focuses on the broadband wave dispersion and requisite considerations for numerical damping, and evaluates the impact of dissipation and space–time discretization schemes for optimal performance. In contrast to conventional methods that employ a plane wave, the proposed approach does not need extra assumptions on the enforcement of boundary conditions and can effectively consider the influences of length scale from the material configurations. A quasi-equiaxed polycrystalline ice microstructure is utilized as an application example for homogenizing heterogeneous materials, in line with advancements in cryo-ultrasonic testing techniques. • The approach combines FE and Green's function analysis to predict wave propagation. • Homogenization uses 3D assumption-free numerical Green functions over complex RVEs. • Key dissipation and discretization parameters for accuracy are reported. • The methodology is tested on polycrystalline ice microstructure. [ABSTRACT FROM AUTHOR]

• The influence of printing parameters, such as filling rate and printing direction, on the mechanical properties of the composite metastructure was investigated via experimental and numerical approaches. • The specific strength and modulus were highest for the sample with a 20 % filling rate with a predominant elastic deformation behaviour. These findings provide a valuable guideline for structural design and manufacturing via 3D printing, where weight-saving and elastic behaviour are considered. • The bending test for samples with different printing directions showed that the printing direction has no significant effect on flexural strength, but the +45°/-45° sample exhibited a slightly higher modulus. • The numerical model can well predict the mechanical properties at higher filling rates (i.e., 100 % and 80 %). The error increased as the filling rate decreased, especially for the samples with 20 % and 14 % filling rates. This paper evaluated the influence of filling rate and printing direction on the mechanical properties of composite metastructure via experimental and numerical approaches. A representative volume element (RVE) and finite element method were adopted to estimate the tensile and flexural properties and verify the applicability of these methods in the 3D printing of composite metastructure. Results showed that apparent tensile and flexural properties drop with decreasing filling rates. The tensile and flexural strength reached 70.7 MPa and 131.1 MPa for solid specimens. The bending test for samples with different printing directions showed that the printing direction of the core has no noticeable effect on flexural strength, but the +45°/-45° sample exhibited the highest modulus. The numerical estimation showed similar trend compared to experimental results for both tensile and flexural properties. Such an attempt indicates the feasibility of designing a composite metastructure with an optimum weight-strength relationship. [ABSTRACT FROM AUTHOR]

Thermal expanding is the important property that defines the stress–strain condition of GRP structures exploited under heating and having limited thermal resistance. So, the GRPs' thermal expanding prediction is the actual requirement of such structures design. The experimental accurate dilatometric study resulted in the non-linearity of thermosetting polymers and plastics thermal expanding under heating. The polymers and plastics thermal expanding coefficient (CTE) is non-linearly increasing under heating before glassing temperature (Tg). Using the previous polymers and GRPs modelling experience and experimental dilatometric results, the non-linear adequate prediction models of their CTE were proposed and proved. The new compensative wave model of polymers' CTE and multi-layer model of GRPs' CTE were proposed and successfully tested. A prediction of the temperature dependences of the thermal expansion coefficients of various thermoset polymer binders and data on the reinforcement structure was performed based on the experimentally obtained temperature dependences of the CTEs of GRPs. The prediction was performed using the finite-element homogenization method in the Material Designer module of the academic version of the Ansys package. A satisfactory concurrence of the numerical results of the prognosis and the experiment for all considered cases is observed in the temperature range from 50 to 100 °C, after glass transition temperature best coincidence of numerical values of CTE is obtained for glass-reinforced plastics on epoxy resin, which were not subjected to thermal aging. [ABSTRACT FROM AUTHOR]

In this study, an effective microscale method based on the parametric modeling scheme of the finite volume method is improved to evaluate the effective thermal conductivity and localized thermal fields of the fiber‐reinforced composites. By comparing with the finite element method and experimental data, it is indicated that the proposed microscale method exhibits a high accuracy in solving their effective properties. On this basis, the mesh sensitivity and fiber volume fraction influence on the thermal conductivity are both investigated. The number of 36 × 36 sub‐cells is employed as the RVE model to balance the computational efficiency and simulating accuracy. In addition, affected by the thermal conductivity and microstructure of constituent materials, the heat flux distribution near the interface between phenolic resin matrix and glass fiber is relatively uniform. The study on the influencing factors of the volume fraction shows that the equivalent thermal conductivity increases slowly at the low volume fraction, while the growth rate of the equivalent thermal conductivity increases significantly at the high‐volume fraction. [ABSTRACT FROM AUTHOR]

Natural fibers are capable substitutes to conventional synthetic fibers, primarily because of their economic and environmental advantages, as well as they find widespread applications in textile, construction, and non‐load‐bearing applications in the case of automotive and aircraft industries. This paper presents a comprehensive review of natural fiber‐reinforced composites, focusing on their failure behavior, failure modelling techniques, and associated theories. Finite element modelling is widely applied in the damage modelling of natural fiber as well as natural fiber‐based green composites. Formation of representative volume elements in conjunction with homogenization emerges to be the common and most effective multi‐scale technique used for determining the effect of microstructures on the thermal and mechanical properties of the natural fiber‐reinforced composite. To provide a better understanding of the insight of damage aspects of natural fiber composites an up‐to‐date review catering to various aspects ranging from its manufacturing techniques, failure processes and mechanisms, finite element modelling techniques, and mechanical performance is very much required. This review aims to address the above‐stated issues, challenges, and details of achievements made with them. [ABSTRACT FROM AUTHOR]

The present study provides a thorough analysis of the influence of filament orientation on the tensile stiffness of 3D-printed structures. This exploration employs a combination of numerical simulations and experimental trials, providing an extensive understanding of additive manufacturing, particularly 3D printing. This process involves layer-by-layer material deposition to produce three-dimensional objects. The examination specifically targets PLA-based 3D printed structures created using Fused Filament Fabrication (FFF) technology and subjects them to rigorous evaluations using a universal tensile testing machine. Additionally, this approach combines Representative Volume Element (RVE) and Classical Lamination Theory (CLT) techniques to extrapolate the mechanical properties of the test material. Although the initial methodology faces challenges in determining the shear modulus with precision, an in-depth investigation results in enhanced accuracy. Furthermore, this study introduces a parametric RVE numerical method, demonstrating its resilience in handling sensitivity to shear modulus. A comparative study of results derived from both the analytical methods and experimental trials involving five series of samples with varied layups reveals that the newly proposed numerical method shows a stronger correlation with the experimental outcomes, delivering a relative error margin of up to 8%.

In this study, the effect of various microcapsule sizes on the mechanical properties of microcapsule-based polymeric materials was investigated using the finite element method and validated with experimental outcomes. Specimens containing 5wt. % of microcapsules were fabricated to calculate the elastic modulus, and maximum tensile stress, and to validate numerical results. To consider the error, five tests were performed for all samples, and results were reported on average. The average errors between the numerical outcomes and experimental results were 4.74% and 5.35% for maximum tensile stress and elastic modulus, respectively. The coaxial electrospraying method was used for synthesizing microcapsules made of alginate (shell) and epoxy (core). A scanning electron microscope (SEM) was used to calculate the diameter of the capsules. To develop an empirical model for the average microcapsule diameter (AMD) and carry out the optimization process, response surface methodology (RSM) with central composite design was used. Also, analysis of variance was employed to validate the accuracy of the model. The effects of three parameters, including voltage, needle size, and the distance between the tip of the needle to the collector, on average microcapsule diameter, were investigated. The empirical model was validated by a confirmation run, and the determined error (1.93%) between the predicted and experimental results indicates the precision of the model. The numerical study indicated that microcapsule-based self-healing polymers containing smaller microcapsules tolerate higher stresses. However, the effect of the microcapsules' size on the elastic modulus of a representative volume element was negligible. [ABSTRACT FROM AUTHOR]

In chemical mechanical polishing (CMP) for IC fabrication, porous pads are critical for achieving extremely consistent throughput in CMP process. The pad hardness, porosity of pad, and pore sizes in the thermoplastic polyurethanes foam fabrication procedure determine the properties of CMP pads. This paper aims to develop a methodology for modeling macro and micro pad hardness. The IC1000 CMP pad has been analyzed with a developed image processing method to determine porosity and pores size. In addition, nano-indentation tests are used to determine physical properties of micro-solid components. For macro hardness analysis, five different sizes of three-dimensional representative volume elements (RVE) have been investigated using the random sequential adsorption technique. Furthermore, simulation of macro pad hardness of RVE models are completed with finite element method. Results of this study not only achieves macro hardness of CMP pad simulation as 3% errors as compared with developed micro-indentation test, but also complete three dimensional porous pad modeling with RVE. [ABSTRACT FROM AUTHOR]

Micromechanics models of composite materials are preferred in the analysis and design of composites for their high computational efficiency. However, the accuracy of the micromechanics models varies widely, depending on the volume fraction of inclusions and the contrast of phase properties, which have not been thoroughly studied, primarily due to the lack of complete and representative experimental data. The recently developed microstructure-free finite element modeling (MF-FEM) is based on the fact that, for a particulate-reinforced composite, if the characteristic size of the inclusions is much smaller than the composite representative volume element (RVE), the elastic properties of the RVE are independent of inclusion shape and size. MF-FEM has a number of advantages over the conventional microstructure-based finite element modeling. MF-FEM predictions have good to excellent agreement with the reported experiment results. In this study, predictions produced by MF-FEM are used in replace of experimental data to compare the accuracy of selected micromechanics models of particulate composites. The results indicate that, only if both the contrasts in phase Young's moduli and phase Poisson's ratios are small, the micromechanics models are able to produce accurate predictions. In other cases, they are more or less inaccurate. This study may serve as a guide for the appropriate use of the micromechanics models. [ABSTRACT FROM AUTHOR]

With the increasing Mach numbers of hypersonic vehicles, extreme aerothermal environments impose substantial challenges on vehicle materials. High thermal conductivity materials facilitate rapid heat redistribution to diminish localized thermal accumulation and reduce material thermal damage, providing a viable route for further enhancing the operational temperature of materials. Here, we successfully fabricate high thermal conductivity C f /HfB 2 -SiC composites through the solid–liquid combination process, achieving an x-direction thermal conductivity of 161.11 W/(m·K), which represents an order of magnitude improvement over traditional carbon fiber-reinforced ultra-high temperature ceramic composites. 3D X-ray computed tomography (CT) is employed to analyze the structural composition of the high thermal conductivity C f /HfB 2 -SiC composites, and the Gaussian Mixture Model is applied to segment the CT images, thus establishing a mesoscale representative volume element (RVE) model based on CT. Combining theoretical models and finite element analysis, we propose a multiscale heat transfer model for high thermal conductivity C f /HfB 2 -SiC composites, which effectively investigates the heat transfer mechanisms of the composites. The fabrication and multiscale heat transfer modeling of high thermal conductivity C f /HfB 2 -SiC composites provide a theoretical basis and guidance for enhancing material performance and design optimization. [ABSTRACT FROM AUTHOR]

Piezoelectric materials can generate an electrical response under mechanical stress, functioning as sensors. Conversely, applying an electrical field to these materials enables precise motion control, making them effective as actuators. Using a proposed methodology, this work focuses on evaluating the effective properties of hybrid multi-oriented composite laminates consisting of structural and piezoelectric layers driven by monoclinic constitutive equations. Square unit cell model was used to calculate all coefficients of the material tensor. The finite element (FE) homogenization method and periodic boundary conditions implemented by node-to-node constraint equations are used to study a representative volume element (RVE) modeled as three-layer unit cell in the mesoscale. The pre-processing, FE analysis, and post-processing are conducted in the FE package ABAQUSⓇ through Python scripts. The computational approach yields results that align closely with the analytical effective coefficients derived from the Asymptotic Homogenization Method (AHM), demonstrating the robustness and accuracy of the proposed methodology. • Evaluation of hybrid multi-oriented composite laminates with piezoelectric layers using monoclinic equations. • FE homogenization with periodic boundary conditions using node-to-node constraint equations in a three-layer mesoscale RVE unit cell. • Numerical methodology shows good agreement with analytical coefficients from Asymptotic Homogenization. • Analysis of stacking sequence influence on the monoclinic constitutive matrix of hybrid laminates. [ABSTRACT FROM AUTHOR]

The elastic properties of a perforated sheet having hexagonal periodic patterns are evaluated using a representative volume element (RVE). The finite element method (FEM) is employed to evaluate the response of the RVE under periodic boundary conditions and numerical homogenisation technique is applied using the FEM solution to estimate the effective properties of the perforated sheet. Numerical homogenisation results are compared to analytical solutions from literature and experimental results. The RVE used in this work considers the radius formed between attached edges and investigates the effect of radius on the overall properties, which has not been sufficiently investigated in literature. Furthermore, the influence of enforcing periodic boundary conditions on the RVE along the thickness direction for such thin perforated structure is investigated. It is found that the elastic constants are overestimated on enforcing periodicity in the thickness direction. [ABSTRACT FROM AUTHOR]

Although the literature is abundant with the experimental methods to characterize mechanical behavior of parts made by fused filament fabrication 3D printing, less attention has been paid in using computational models to predict the mechanical properties of these parts. In the present paper, a numerical homogenization technique is developed to predict the effect of printing process parameters on the elastic response of 3D printed parts with cellular lattice structures. The development of finite element computational models of printed parts is based on a multi scale approach. Initially, at the micro scale level, the analysis of micro-mechanical models of a representative volume element is used to calculate the effective orthotropic properties. The finite element models include different infill densities and building/raster orientation maintaining the bonded region between the adjacent fibers and layers. The elastic constants obtained by this method are then used as an input for the creation of macro scale finite element models enabling the simulation of the mechanical response of printed samples subjected to the bending, shear, and tensile loads. Finally, the results obtained by the homogenization technique are validated against more realistic finite element explicit microstructural models and experimental measurements. The results show that, providing an accurate characterization of the properties to be fed into the macro scale model, the use of the homogenization technique is a reliable tool to predict the elastic response of 3D printed parts. The outlined approach provides faster iterative design of 3D printed parts, contributing to reducing the number of experimental replicates and fabrication costs. [ABSTRACT FROM AUTHOR]

This article investigates the performance of the XFEM for stiff embedded interfaces and inclusions. It is known that the XFEM may lead to ill‐conditioned stiffness matrices and oscillations in the interface traction field, the severity of which depends on the underlying basis functions, as well as on the orientation of the interface. The jumps at the discontinuity are shown to contain quadratic bubble residuals that can introduce oscillatory behavior. Those residuals are worsened by the ill‐conditioning of the system with very stiff interfaces. A variationally consistent method is proposed to overcome the oscillatory behavior and ill‐conditioning, in which the assumed strain method is developed to directly eliminate bubble residuals and deploy Legendre polynomials and explore their orthogonality properties to improve the conditioning of the stiffness matrices. Numerical examples illustrate the efficiency and generality of the proposed approach at both element and structural levels. The new approach is shown to be robust for imposing Dirichlet type boundary conditions at the crack interface, such as crack closure and initially rigid cohesive laws. The effects of numerical oscillations on the prediction of effective properties of composites in XFEM‐based computational homogenization procedures are also discussed. [ABSTRACT FROM AUTHOR]

Copyright of Acta Materiae Compositae Sinica is the property of Acta Materiea Compositae Sinica Editorial Department and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Particle reinforced metal matrix composites have complex meso-structure.The construction of its geometric model is a challenging work in the research of its mechanical properties.Through the Python language interface of the ABAQUS software, the parametric modeling of the complex mesoscopic model of particle reinforced metal matrix composites was realized and encapsulated into a plug-in.The plug-in can construct the axisymmetric unit cell model, the three-dimensional periodic unit cell model and the randomly distributed representative volume element model.The effect of zirconia toughened alumina particles (ZTA) on the mechanical properties of zirconia toughened alumina particles reinforced iron matrix composites (ZTAp/Fe45) was analyzed.The results shows that the strengthening effect of irregular polyhedral particles on the elastic modulus of the composites was greater than that of spherical particles.However, the irregular morphology of ZTA resulted in more stress concentration in the composites.With the increase of ZTA particle volume fraction, the elastic modulus of ZTAp/Fe45 composites shows an upward trend, which indicates that the elastic properties of composites can be effectively improved by adding reinforced particles.In the case of low interfacial modulus, the improvement of interfacial bonding properties can significantly improve the elastic modulus of composites.After the interfacial modulus reaches the matrix modulus, the effect of increasing interfacial modulus on the elastic modulus of composites gradually slows down.

A coupled micro–meso-scale modeling strategy is proposed to investigate the damage mechanism of 2D SiC/SiC ceramic matrix composites. The multi-scale modeling begins with microstructure construction using the representative volume elements (RVE). The effective properties of the SiC/SiC yarn are computed using the micro-scale RVE model. At meso-scale, the Tsai-Wu and Mohr's failure criteria are used to describe the different failure modes of yarn and matrix. A satisfied agreement with experimental results obtained by uniaxial tension tests validates the proposed multi-scale modeling strategy. The damage behavior of 2D SiC/SiC composites under in-plane shear loading is further investigated. [ABSTRACT FROM AUTHOR]

This paper presents an analysis on the elastic characteristics of luffa and palm natural fiber composites (NFC) with epoxy and ecopoxy matrixes, taking into account the impact of fiber volume fractions. Furthermore, longitudinal modulus, transverse modulus, shear modulus, and Poisson's ratio were predicted using representative volume elements (RVEs) with chopped random and unidirectional fiber arrangements. However, analytical approaches such as rule of mixture, Chamis, Halpin–Tsai, and Nielsen were considered for validating and comparing the findings of finite element analyses. Hence, it was found that increasing fiber volume fraction increased the elastic properties of palm/epoxy, palm/ecopoxy, and luffa/epoxy NFCs, but decreased that of luffa/ecopoxy NFC. Addition of palm fibers in ecopoxy and epoxy had stronger effect than luffa on enhancing the elastic properties of the final structure. However, greatest elastic characteristics observed through analytical and numerical models were obtained for ecopoxy matrix with 0.5 palm fibers. A strong agreement was observed between the results obtained from analytical approaches and RVE unidirectional model. Chamis model exhibited higher outcomes compared to the considered analytical techniques, while Halpin–Tsai model showed the least values. [ABSTRACT FROM AUTHOR]

In recent years, natural fiber composites have attracted attention as a potential structural material. This study evaluates the effective elastic properties of sisal fiber-reinforced polystyrene composites analytically and numerically using a numerical homogenization approach. The experimental result obtained was compared with the phenomenological models and finite element analysis predictions. The study indicates that the effective elastic properties of sisal fiber-reinforced polystyrene composites are affected by parameters such as fiber loading, cross-sectional area and RVE. [ABSTRACT FROM AUTHOR]

This study presents a systematic model to optimise nano-silica utilisation in cement paste and predict its nonlinear behaviour. The model integrates a hydration model, which calculates the dissolution rate of each clinker mineral, with a thermodynamic model that simulates the hydration reaction and interaction between hydrates and nano-silica. The investigation considered different replacement levels of nano-silica (2 and 4% by weight of cement) to analyse the phase assemblages and porosity of nano-silica reinforced cement paste. The reaction between nano-silica and the hydrate (portlandite) was meticulously accounted for by incorporating the formation of calcium-silica-hydrate (C-S-H) with a realistic transition from jennite-type C-S-H (Si/Ca ratio of 0.58) to tobermorite C-S-H (Si/Ca ratio of 0.67). The coupled model was validated against the experimental results obtained from thermogravimetric analysis, X-ray diffraction, and scanning electron microscopy, ensuring its reliability. Subsequently, the model was used to compute the volume fractions of various phases including hydrates, unhydrated clinkers, pores, and unreacted nano-silica. A representative volume element (RVE) was formulated for the cement pastes with and without nano-silica using MATLAB. The RVE was further evaluated through finite element analysis using COMSOL Multiphysics, enabling the computation of homogenised material properties such as compressive strength, and this aligned well with experimental findings. In summary, the proposed systematic model provides a realistic prediction of the nonlinear behaviour of cement pastes with different nano-silica replacement levels. Its applicability extends to the optimisation of cement-based composites for diverse engineering applications. • Experimental validation confirms the nucleation and pozzolanic impact of nano-silica in cement paste. • Successful integration of the pozzolanic effect within the coupled hydration and thermodynamic model. • Accurate predictions of volume fractions for hydrates, unreacted clinker, pores, and unreacted nano-silica. • Development and analysis of nano-silica reinforced cement paste's RVE for nonlinear mechanical behaviour. [ABSTRACT FROM AUTHOR]

[Display omitted] • The 3D representative volume element of semi-flexible pavement (SFP) material can accurately predict the uniaxial compressive strength and stiffness of SFP. • High-strength, low-modulus materials improve SFP mechanical properties by harmonizing cement and PA deformation. • The SFP properties can be improved by strengthening the interface properties, until a certain threshold value. • Aggregate modulus has no significant effect on the compressive properties of SFP, but higher modulus asphalt mortar significantly improve them. Semi-flexible pavement (SFP) material is a composite comprising cement, coarse aggregates and asphalt mortar, which has complex mechanical properties. Traditional experimental methods struggle to accurately quantify the effect of each phase and their interfaces on the SFP's mechanical properties. Micromechanical modelling based on finite element method offers a promising solution. In this study, a new micromechanical model for SFP is proposed, idealizing the material by representative volume elements. SFP mesostructure is represented as a simplified five element composite consisting of cement, asphalt mortar, aggregate, pore and cement-asphalt mortar interface. Periodic boundary conditions are used to simulate an infinite repetitive structure within a finite computational domain. The resulting model allows evaluating the stiffness and damage resistance of SFP in a computationally efficient manner. This model is utilized to explore the mechanical properties of SFPs and the results are compared with the experimental findings. The results show that the model captures the uniaxial compressive strength and stiffness for all materials examined. The model is further used to evaluate the effect of properties of individual elements of SFP on its stiffness and strength. The feasibility of using the proposed modelling approach to optimize the material design of SFP is discussed. [ABSTRACT FROM AUTHOR]

• An algorithm to generate microstructures with randomly wavy fibers is proposed. • The algorithm can generate fibers ranging from straight to complex wavy shapes. • Fibers are geometrically characterized by their tortuosity, spread and orientation. • Embedded elements of finite element analysis are used to perform homogenization. • A framework for micromechanics of composites with wavy fibers is presented. During multiscale modeling and analysis of composite materials, accurately capturing the distinctive microstructural features of the material is essential. This is achieved by generating a representative volume element (RVE). Fiber reinforcements in composites can exhibit various shapes, including straight, slightly wavy, or complex shapes, depending on the inherent properties or the manufacturing process. Fibers are characterized based on their tortuosity, spread, and orientation distribution. It is crucial to account for these geometrical attributes during the microstructure generation and subsequent micromechanics modelling as they significantly influence the effective properties of the composite. The present work describes a novel algorithm capable of modeling a broad range of 3D periodic microstructures with fibers having random waviness. The effects of various parameters in the algorithm are studied to understand their influence on fiber shapes. This is followed by finite element analysis of the generated RVEs using the embedded element technique to quantify the microstructure- mechanical properties relationships. Finally, guidelines on the usage of the proposed model to generate fibers with desired microstructure is elucidated. A comprehensive framework for modeling and analyzing microstructures with complex fiber geometry is outlined. [ABSTRACT FROM AUTHOR]

Recent researches show that the embedment of hollow spheres in the matrix phase of composite materials improves the strength of these structures against crack propagations. Rare studies are reported for calculating equivalent elastic constants of fiber reinforced composites containing hollow spheres. In this paper, the effects of hollow spheres on mechanical characteristics of fiber reinforced composite are studied for the first time. To achieve this aim, a micromechanics based finite element method is employed. Representative volume elements (RVEs) including hollow spheres with different radius, thickness and volume fraction of hollow spheres, are modeled by using 3D finite elements. The equivalent elastic constants are calculated through homogenization technique. The results are compared with available experimental works. Good agreements find between two sets of results. Also, the volume fraction, number and thickness of hollow spheres as effective parameters on mechanical properties of composite were investigated. The results show the equivalent elastic properties increase with increasing the volume fraction and number of hollow spheres and decrease with increasing the number of hollow spheres. Furthermore, the equivalent Young's modulus in transverse directions to the fiber direction and shear modulus of the composite increase with increasing the thickness of hollow spheres. As a final result, the presence of hollow spheres in the matrix phase generally increases the equivalent elastic constants without significant changes in the weight of structures. [ABSTRACT FROM AUTHOR]

In the present study, Composite material consisting of an elastic homogeneous isotropic matrix in which are embedded coated elastic isotropic inclusions, widely used in many applications is investigated by a homogenization approach coupled to the finite element method. A finite element model is proposed to predict the Young's and shear modulus of the three-phase composite containing spherical inclusions surrounded by a spherical or ellipsoid interphase layer. Three cases of particle volume fractions and interphase were considered with the addition of two interphase morphologies. Young's modulus of the interphase region was varied from soft to hard than the matrix properties. We note the interphase morphology and properties play an important role in the elastic properties of composite with increasing the volume fraction of inclusions and interphase. The results were compared to the first-order bounds Voigt and Reuss, and the mean-field homogenization techniques. A sensitive study of the effect of mesh density on the results of the von Mises stresses and elastic properties has been made. [ABSTRACT FROM AUTHOR]

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